西沙海槽潜在天然气水合物成因及形成地质模式  

ORIGIN AND GENETIC MODEL OF POTENTIAL GAS HYDRATES IN XISHA TROUGH,SOUTH CHINA SEA

作　　者：王宏语[1] 孙春岩[1] 张洪波[1] 牛滨华[1] 

机构地区：[1]中国地质大学能源学院,北京100083

出　　处：《海洋地质与第四纪地质》2005年第4期85-91,共7页Marine Geology & Quaternary Geology

基　　金：国家高新技术研究开发规划项目(820-03-02);国家重点基础研究发展规划项目(G2000046705)

摘　　要：西沙海槽具备良好的热解成因气及断层通道、深部异常压力等运移条件,分析海底表层沉积物所含甲烷气来源可以很好地指示潜在天然气水合物成因。西沙海槽海底表层沉积物所含甲烷气以热解成因气为主,可能混有少量生物成因气。表层沉积物所含甲烷气为断层渗逸-自由扩散作用双重运移结果,主要有3种来源:(1)直接来自于下部断层通道中气态烃的释放;(2)来自于动态变化的水合物分解,再由渗滤作用或沿浅部微小断层向上运移;(3)来自于原地少量的生物气。不同地区有不同的气体来源,这是海底表层沉积物甲烷高值区与下部断层相关性较大而与BSR区域并非完全一致的原因。甲烷气来源及运聚条件综合分析表明,潜在天然气水合物以热解成因为主,为断层-渗滤综合地质模式。Xisha Trough region has favorable thermogenic gas source, structural path,and deep pressure migration conditions. The origin of methane gas contained in the seafloor superficial sediment can indicate the genesis of potential gas hydrate. Through methane carbon isotope testing and gaseous hydrocarbon parameter calculation, we found that the methane gas contained in seafloor superficial sediment of Xisha Trough mainly came from deep thermogenic gas, and small quantity of gas from biogenic methane gas. The analysis of migration and accumulation conditions indicates that methane gas migration is a comprehensive fashion composed of fault filtration and free diffusion differentiation, and there are three methane gas sources：① gas that directly releases from gaseous hydrocarbon in the deep fault path;②gas that comes from dynamically changeable hydrate decomposition and migrates upward under the action of filtration or along a small and shallow fault;③biogenic gas in the shallow layers. Different regions have different gas sources, so regions of high values of methane gas are not completely consistent with BSR region, but correlative to deep large faults. Origin, migration and accumulation fashion of methane gas indirectly indicate that potential gas hydrate in Xisha Trough is thermogenic, and genetic model is comprehensive fault-filtration geologic model.

关 键 词：天然气水合物 甲烷气 热解成因 地质模式 西沙海槽 

分 类 号：P744.4[天文地球—海洋科学]